Seasonal and diurnal flight activity patterns in some species of black-flies (diftera: simdliidae)

Abstract

The flight activity of three species of Simuliidae was studied in the Eden Valley, Cumberland. The flies were caught using a net mounted on a vehicle, which was driven at 48 km/h along a circuit, consisting of four roads parallel to the River Eden (at distances of 0.5, 1.5, 5.0 and 6.0 km from the river), and the main road at right angles to the river, between the villages of Langwathby and Melmerby. Equipment in the back of the vehicle allowed the flow of insects from the net to be divided into catches, each of which was caught over a distance of 1 km. An anemometer on the mouth of the net allowed the insects to be calculated as a concentration, so that the catches on the four roads could be directly compared. The female flies were all dissected and thus divided into different physiological groups. The main divisions were into nulliparous and parous flies, each of which was sub-divided into blood-thirsty and blood-fed flies, and into gravid and parasitised flies. The diurnal rhythm of the three simuliid species was studied, noting the differences between the different physiological groups. The effect of the weather on these rhythms was examined. By comparing the four parallel roads, the spatial distribution of the three species was studied. The distribution, and thus powers of dispersal, of the nulliparous and parous flies was compared, and the effect of the presence of parasites on this ability to disperse was noted.